The invention relates to a control device and to a method for controlling a polyphase DC-to-DC voltage converter, in particular using a phase-shift interleaved control.
DC-to-DC voltage converters, that is to say converters which convert a DC input voltage into a DC output voltage, are often driven using current hysteresis control. For this purpose, the current, for example in an inductor of the DC-to-DC voltage converter, is controlled using a three-state controller. In this case, voltage is applied to the inductors at intervals if the inductor current drops below a first threshold value and voltage is taken from the inductor if the current rises above a second threshold value. As a result, the current in the inductor can always be kept within the current value range defined by the first and second threshold value, and the output voltage of the DC-to-DC voltage converter can be controlled.
DC-to-DC voltage converters are often designed to be polyphase. In this case, the total output voltage of the DC-to-DC voltage converter is composed of the two output voltages of the parallel-connected converter branches. In order to reduce the current ripple of the input current and the voltage ripple of the total output voltage, a phase-shift interleaved actuation (“interleaved control”) can be used. In this case, the individual converter branches are actuated with a phase shift.
By means of said actuation, it is possible for the current ripple or voltage ripple of the individual converter branches to mutually cancel out, that is to say negatively interfere, and hence reduce the total current or voltage ripple. This leads to lower loadings in voltage source and load and to reduced implementation expenditure and more cost-efficient configuration of filtering devices within the converter.
In order to quickly achieve an optimum phase shift between the converter branches or after achieving it, keeping it at precise as possible, it is necessary to take measures to be able to control and regulate the phase shift between the converter branches.
The document Schellekens, J. M. et al.: “Interleaved Switching of Parallel ZVS Hysteresis Current Controlled Inverters”, The 2010 International Power Electronics Conference, IEEE, 21-24 Jun. 2010, pp 2822-2829 discloses a method for current hysteresis control for DC-to-DC voltage converters which is based on the generation of threshold value ramps for generating a phase shift.
The document U.S. Pat. No. 7,522,436 B2 discloses a DC-to-DC voltage converter with parallel-connected phases which are actuated in a master-slave mode. In this case, firstly, a master phase is determined and, for the slave phases, a ramp function is calculated for the upper current threshold value, which ramp function implements a particular linear variation of the upper current threshold value over a switching cycle.
There is therefore a need for possibilities for generating and permanently reliably maintaining a phase shift in converter branches, which are controlled using an interleaved controller, of a polyphase DC-to-DC voltage converter in a simple, flexible, reliable and quickly reacting manner.